Influence of Absorbing and Non-Absorbing Coating on Black Carbon Optical Properties at Different Coating Thickness

In this study, the effect of coating material and coating thickness on the variations in coated black carbon (BC) optical properties has been studied at an incident wavelength of 0.55 μm. The simulation has been performed based on the core-shell Mie theory model for BC in the accumulation mode under various coating conditions. Six coating materials, non-absorbing and strongly absorbing spices produced from three different sources of burning emissions, have been considered: (1) sulfate, (2) nitrate, (3) non-absorbing organic aerosols and organic aerosols descent from, (4) Hardwood OAK fuel, (5) Pocosin Pine fuel, and (6) Galberry OCG fuel. For each mixing state, the variations in extinction, scattering, absorption efficiencies, single scattering albedo, and absorption enhancement have been evaluated for five values of the relative coating thickness R = 1.1, 1.5, 1.9, 2.3, and 2.7. The simulation results show that the thicker the coat the more the absorption efficiency gets reduced. The scattering efficiencies are almost enhanced when BC is coated by non-absorbing materials. For the absorbing materials (BC coated by absorbing shells), the absorption enhancement is more important than for non-absorbing species (BC coated by non-absorbing shells) and ranges within (1.085–2.352) and (1.109–6.288), respectively. The present results may be useful for understanding the dependence of optical properties of coated aerosol on physical and optical properties of both core and shells.